1. Field of the Invention
This invention relates generally to transducer diaphragms and more particularly to the use of chemical etching to create different thickness patterns on the diaphragm plate to change the location of maximum strain amplitude on the plate for monitoring by overlying strain gauges.
2. Description of the Prior Art
Various methods have been employed in the past to improve the performance of strain gauge/diaphragm type pressure transducers, particularly with respect to the location of the strain gauges bonded to the diaphragm to measure the tensile (expansion) and compressive (contraction) strain of the diaphragm when it is subjected to stress in the form of pressure exerted against the diaphragm. Unfortunately, many of such prior manufacturing techniques have become impractical due to the increasing cost of manufacture and the complicated steps that have been employed.
The problem is particularly acute in connection with low pressure/small diameter diaphragm type transducers which incorporated integrally bonded strain gauges on the diaphragms. The size of the gauges and their location on the diaphragm are of primary importance in connection with output/input efficiency, stability/time performance, and the effort to obtain linearity and to minimize hysteresis problems. This is accomplished by placing the center of one or more strain gauges to coincide with the center of the maximum amplitude of the tensile strain locations, and another set of gauges to overlie a corresponding center for maximum amplitude of compressive strains. In the past a primary problem has arisen with the maximum compression amplitude which is typically at the very outer edge of a conventional diaphragm. Those methods which have sought to distribute this maximum compressive strain location inwardly toward the center have invariably added excessively to the cost of the process and are therefore rather impractical, as well as somewhat unreliable.